1. Field of the Invention
The present invention relates to a fuel cell formed by sandwiching an electrolyte electrode assembly between a pair of separators. The electrolyte electrode assembly includes a pair of electrodes and an electrolyte interposed between the electrodes. Reactant gas flow fields are formed along electrode surfaces, and reactant gas passages for flowing reactant gases through the fuel cell in the stacking direction.
2. Description of the Related Art
For example, a polymer electrolyte fuel cell employs a membrane electrode assembly (electrolyte electrode assembly) which includes an anode, a cathode, and an electrolyte membrane interposed between the anode and the cathode. Each of the anode and the cathode comprises an electrode catalyst layer and porous carbon. The electrolyte membrane is a solid polymer ion exchange membrane. The membrane electrode assembly and separators (bipolar plates) sandwiching the membrane electrode assembly make up a unit of a power generation cell for generating electricity. In use, normally, a predetermined number of power generation cells are stacked together to form a fuel cell stack.
In general, the fuel cell has so called internal manifold structure in which supply passages and discharge passages extend through the separators in the stacking direction. The fuel gas, the oxygen-containing gas, and the coolant flow from the respective supply passages to a fuel gas flow field, an oxygen-containing gas flow field, and a coolant flow field, and then, the fuel gas, the oxygen-containing gas, and the coolant are discharged into the respective discharge passages.
For example, in a process control apparatus disclosed in Japanese Laid-Open Patent Publication No. 6-218275, as shown in FIG. 22, two plates 1a, 1b are overlapped with each other, and stacked alternately with a unit 2. The unit 2 includes an anode 2b, a cathode 2c, and an MEA 2a interposed between the anode 2b and the cathode 2c, and these components are sandwiched between a pair of contact plates 2d. 
A first chamber 3a is formed between the plate 1a and the unit 2, a second chamber 3b is formed between the plate 1b and the unit 2, and a third chamber 3c is formed between the plates 1a, 1b. A passage 5 extends through ends of the plates 1a, 1 with packings 4.
The passage 5 is connected to, e.g., the second chamber 3b through a flow field 6 formed between the plates 1a, 1b. Though not shown, two other passages extending in the stacking direction are provided, and the two passages are connected to the first chamber 3a and the third chamber 3c through flow fields between the plates 1a, 1b. 
In the conventional technique, the plate 1b has holes 7 to form the flow field 6 connecting the passage 5 extending in the stacking direction to the second chamber 3b. Likewise, the plates 1a, 1b have holes connecting the two other holes to the first chamber 3a and the third chamber 3c. 
However, as described above, since the holes 7 or the like are formed in the plates 1a, 1b as separators, many steps are required for fabricating the separators, and the structure of the separators is complicated. Further, in the case where metal separators are used, since metal portions around the holes are exposed, insulating processing needs to be applied to the areas around the holes. Thus, a large number of steps are required for fabricating the metal separators uneconomically.